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Cooper Tire's Discoverer AT3 4S

Cooper's Discoverer AT3 4S proved to be a capable on- and off-road tire that's designed for utility vehicles and pickup trucks.

Photo by Kelly Bracken.

Cooper Tire & Rubber Co. is in the midst of an aggressive refresh of its tire lineup. Earlier this week, Brad Hughes, president and chief executive, told investors the company will release 18 new products in the coming 24 months to boost digital sales.

The aggressive product refresh is already underway, as the company has released several new tires this year, including its Discoverer AT3 line – it replaces the Discoverer A/T3 line – that includes the 4S, LT, and XLT trio for sport utility vehicles, light pickups, and heavy-duty pickups. The all-terrain tires are designed for on- and off-road driving.

WorkTruckOnline.com recently field-tested the 4S tire in various conditions in Southern California's Coachella Valley on the pavement of U.S. interstates and local roads, as well as the rocky and sandy trails of San Bernardino and Riverside counties. After fitting them to a 2015 Jeep Grand Cherokee 4x4, we drove more than 740 miles on the tires, and would give them high marks.

We should mention that Cooper is positioning Discoverer AT3 as a highly capable choice for winter driving with features that increase grip on wet surfaces and capability to handle light snow. Since we didn't test in those conditions, take that as a caveat.

The 4S is available in 44 sizes from 15- to 22-inch wheel dimensions. It includes Cooper's Adaptive-Traction technology, which means the tire provides grip on various driving surfaces and in hot or cold weather.

Here's a closer look at the sidewall.

Photo by Kelly Bracken.

Increased traction comes from a silica-based tread compound and the company's Sure-Grip five-rib pattern. Zigzag sipes at the tire's edge increase traction and stability. Grooves in the ribs are designed to reduce hydroplaning. A saw-tooth pattern in the ribs traps snow in the tread and improves stopping distance on snowy surfaces. The sidewall carries a Three-Peak Mountain Snowflake (3PMSF) symbol indicating that it performed well in the American Society for Testing and Materials' traction tests on packed snow.

Adding an off-road tire to your pickup truck or midsize SUV comes with the assumption that your fuel economy will slip, and that was the case for the parts of the drive that were more gridlocked. We lost about 1-2 mpg in stop-and-go driving, but the tires delivered an improvement of 1-2 mpg at cruising speeds on the eastbound Interstate 10 heading out of Los Angeles County.

We filled the tires with air, rather than nitrogen, and began our test with all four tires at 36-37 psi. That gradually increased to 42-43 psi as we tested the tires on the dirt and rocky off-road trails of Joshua Tree National Park on an early August day when the desert heat reached 115 degrees.

After warming the tires up on the dusty road leading toward Keys Ranch in the northwestern section of the park, we headed for Geology Tour Road – an easy 17.1-mile drive that alternated hard-packed dirt with some loose sand and small rocks. The 4S tires provided plenty of stability, even on the narrower one-way loop on the southern-most section that added a few bumps.

Next, we headed for the Black Eagle Mine Road, another easier drive in the eastern lower-elevation section of the park that leads to a private iron-mining operation. The 24-mile road was wide open for most of the run with some rocky flood channels that cut across the road. The last third also includes several short steeper sections to traverse. The tires ably crawled across these loose rocks and provided traction on stretches where the road had crumbled away.

We tested the Discoverer AT3 4S on the off-road trails of Joshua Tree National Park.

Photo by Paul Clinton.

We finished the day on a stretch of Old Dale Road, an intermediate 26.3-mile trail with the same starting point as Black Eagle Mine Road. About eight miles in, we lost some stability in very spongy, deeper sand on the wide open road, so we headed back. A smaller vehicle or perhaps the LT tires could have helped in this situation.

When we returned to home base, we noticed a few smaller rocks in the tread, but not many.

Overall, the Cooper AT3 Discoverer 4S tires offered very capable traction without a significant on-road fuel-economy penalty. They would make a good choice for fleets that need a tire for vehicles that do most of their mileage on pavement but need occasional off-road capability.

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